i had a problem with my combo, turned out the dust cap had a dang in it, and partly the glue was loose. resulting in huge resonance at high volumes, because of the dust camp hitting some piece of cardboard. i pulled off the cap for about a thirht of the way, and put the cap back in shape. its fine now, but i think i need to glue the cap back. what kind of glue should i use? some dutch amp builder recommended contact glue, so i got some, but there where different kinds. what is the correct type of glue?